I would have to think the $40 million figure he mentioned would refer to whatever phase of the project was to be filmed there, or what the economic impact on Cleveland would be, something along those lines. Unless Joss has decided to do most of the action sequences with Hot Wheels and puppets. Hey, we know he makes a mean puppet, I'd give him the benefit of the doubt.

Were there any other Marvel movies that could have been considering Michigan down the line?

It's sort of weird that the governor seems to mention a single superhero. Granted he also mentions a cape so that's presumably an archaic riff rather than him being totally clueless about what project it is. I'd be pleased if they took Runaways off hold and secretly fast-tracked it though.